How to affect particle size over time?
Here is the method to increase the particles size through time, as explained by BlenderShortTests in one of his tutorials:

Select your emitter and go to Properties &gt; Particles, click New.
In Properties &gt; Particles &gt; Render, click Object and choose the object that will be emitted as particles and its size.
Go to your 3D view and press alt A to launch a preview of your emission animation, then stop it somewhere in its course.
In Properties &gt; Particles &gt; Textures, add New and give it a name.
In Properties &gt; Textures &gt; Type, choose Blend.
In Properties &gt; Textures &gt; Colors, click Ramp.
In Properties &gt; Textures &gt; Mapping &gt; Coordinate &gt; choose Strand/Particles.
In Properties &gt; Textures &gt; Influences, unclick Time and enable Size.
In Properties &gt; Textures &gt; Colors, play with the Ramp controller to increase or decrease the size of your emitted object through time.

The video also explains how to make a fade out effect on the particles: https://www.youtube.com/watch?v=67024UyCZ6A